Harbor porpoises (Phocoena phocoena vomerina) catching and handling large fish in the U.S. West Coast
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Harbor porpoises (Phocoena phocoena
vomerina) catching and handling large
fish in the U.S. West Coast
Cindy R. Elliser1, Sanne Hessing2, Katrina H. MacIver1, Marc A. Webber3, and William Keener3
1 Pacific Mammal Research, 2 CetaScience, 3 The Marine Mammal Center
Elliser, C.R., Hessing, S., MacIver, K.H., Webber, M.A., and Keener, W. (2020). Harbor porpoises (Phocoena phocoena vomerina) catching and handling large fish on the U.S. West Coast. Aquatic Mammals 46(2): 191-199.
What’s for dinner?
• Globally harbor porpoises generally
feed on small prey (< 30 cm)
• In the Salish Sea common prey are
• Pacific Herring
• Walleye Pollock
• Pacific Hake
• Pacific Sandlance
(species common to Walker et al. 1998 & Nichol et al. 2013)
What’s for dinner?
• However large prey consumption
has been documented
• (in mass and/or length up to 63 cm)
• No previous knowledge of this behavior
along the U.S. West Coast
• Information is limited on harbor
porpoise foraging ecology/behavior
(Fontaine et al. 1994; Aarefjord et al. 1996; Víkingsson et al. 2003; Sveegaard et al. 2012; Andreasen et al. 2017)
Observations
• Land based behavioral studies:
• Salish Sea, Washington; Pacific Mammal
Research
• San Francisco Bay, California; The Marine
Mammal Center
• Stranding:
• Cook Inlet, Alaska; Alaska Stranding
Network/NOAA/NMFS
Observations • Burrows Bay • 7 August 2017 • Salmon sp. (Oncorhynchus sp.)* • Fish capture • Fish carried sideways *W. Walker, pers. comm., 21 February 2019
Observations • Burrows Bay • 12 August 2017 • Salmon sp. (Oncorhynchus sp.)* • Fish capture • Fish thrown in air *W. Walker, pers. comm., 21 February 2019
Observations • Burrows Bay • 25 July 2019 • Coho salmon (Oncorhynchus kisutch)* • Fish capture • Fish carried sideways *W. Walker, pers. comm., 21 February 2019
Observations • San Francisco Bay • 17 November 2017 • American Shad (Alosa sapidissima)* • Fish capture • Fish carried sideways *J. Ervin, pers. comm., 13 July 2019
Observations • San Francisco Bay • 17 November 2017 • American Shad (Alosa sapidissima)* • Fish capture • Fish carried sideways *J. Ervin, pers. comm., 13 July 2019
Observations
• San Francisco Bay
• 19 October 2016
• American Shad (Alosa
sapidissima)*
• Female harbor porpoise with
calf
• Fish carried sideways
*J. Ervin, pers. comm., 13 July 2019Observations • Cook Inlet, Alaska • 8 August 2014 • Pink salmon (Oncorhynchus gorbuscha) • Consumption/regurgitation • Lactating female harbor porpoise (dead/by caught)
Big dinner! – even if consuming juvenile/sub adult
• American shad • Salmon species
• Females: 61.6 cm • Average for 5 species
• Males: 50 cm commonly found in Salish Sea
• Weight up to 5,500g • 53.8 cm to 80.0 cm
• Wet weight 1,858 to 7, 807 g
• Dorsal spines
US Fish and Wildlife
O’Neill et al. 2014New prey species for U.S. West Coast harbor
porpoises
• American shad: not a previously known harbor porpoise prey species
• U.S. West Coast (where it is non-native) or
• U.S. East Coast (where it is native)New prey species for U.S. West Coast harbor
porpoises
• Salmon species:
• Known prey species in the Atlantic
• Gulf of St. Lawrence
• Scandinavia
• West Greenland
• Baltic Sea
• This is the first documentation for the U.S.
West Coast
Fontaine et al., 1994; Aarefjord et al., 1996; Heide-Jørgensen et al., 2011; Andreasen et al., 2017What are the benefits?
• Harbor porpoises have a high metabolic rate, but limited in the amount
of energy they can carry
• Big fish, big caloric intake:
• Fish mass is cubic function of fish length, and the caloric value of the fish is a
product of their mass
• More important for pregnant/lactating females due to increased energetic needs?
Kanwisher & Ridgway, 1983; Brodie, 1996; MacLeod et al., 2007; Gallagher et al., 2018; Rojano-Doñate et al., 2018; Booth, 2019Risky Business: Eyes bigger than their stomach?
• Asphyxiation of harbor porpoises has been documented
• German and Irish waters: Scad (Trachurus churus) , sole (Solea solea) and cod
(Gadus morhua)
• Outer coast of Washington: American shad
• San Francisco Bay: Smooth Greyhound shark (Mustelus californicus)
• Risk can increase due to large size and/or species with dorsal spines
Orr, 1937; Scheffer & Slipp, 1948; Scheffer, 1953; Stolen et al., 2013; Ryan & Bolin, 2014Conclusions
• Harbor porpoises are likely consuming large prey items
• American shad and salmon species should be listed as prey items
• Understanding type and size of prey is critical to better understand foraging
ecology
• Behavior may be seen more often in pregnant and/or lactating femalesSupporting evidence
• Current work: PacMam and colleagues
• Documenting asphyxiation cases along CA, OR, and WA
• Almost all fish were American shad
• Almost all of the harbor porpoises were females – most were reproductively
activeMore research is needed! • Wild harbor porpoise behavior remains poorly understood – reports such as these are needed to fully understand their behavioral repertoire and ecological relationships
Thank you! Acknowledgements We thank Steve Elliser, Linda Rogers, Kathy Burek, James Ervin, James A. Hobbs, Levi Lewis, NOAA NMFS Alaska Stranding Network, William Walker, Annemarie van den Berg, and Eligius Everaarts for their support, help, data, and personal communications. Funding was provided by the Orange County Community Foundation and the Andeavor Community Foundation Paper is open access: Elliser, C.R., Hessing, S., MacIver, K.H., Webber, M.A., and Keener, W. (2020). Harbor porpoises (Phocoena phocoena vomerina) catching and handling large fish on the U.S. West Coast. Aquatic Mammals 46(2): 191-199.
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